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What are these bars on an F-16's nose?
I've always wondered what the purpose of these "bars" on the nose of the F-16 (and some other military aircraft) are. Are they sensors (if so, what kind)? Are they lightning strips? I can't seem to figure out how to word my search query to find an answer, so I figured I'd ask here!

Source: af.mil

What are "lightning strips" that you hypothesize? All google turns up are decorative or sanding products.  Did you possibly mean "lighting"?  Like landing lights that are visible from forward, but don't shine into the pilot's eyes?

@PeterCordes What's being referred to there are discussed here: https://aviation.stackexchange.com/q/25020/7532. Obviously that isn't the correct answer, but as a first guess it's a reasonable one.

These are antennae for the IFF (Identification Friend or Foe) system.  IFF is a system to help distinguish friendly aircraft from unfriendly ones.

This particular antenna arrangement is used on only a couple of F-16 models. The first was the F-16 Air Defense Fighter (ADF) version. This model was converted from the F-16 Block 15 for use as a fighter interceptor for the US Air National Guard. A total of 271 F-16A and F-16B aircraft were upgraded to this standard between 1989 and 1992. One of the modifications made during the conversion process was installation of the Teledyne/E Systems Mk.XII Advanced IFF system, given the designation APX-109. This system included four antennas, often nicknamed "bird slicers," placed in front of the cockpit canopy with additional antennas on the bottom of the inlet.

From: http://www.aerospaceweb.org/question/planes/q0286b.shtml

Also, to add to Wayne's answer, there are multiple antennas because the computer that processes the data received compares the phase of the signals received from each of them to calculate the direction the signal came from... Because they are separated from one another, any signal received from a point directly in front of them will be received at the same time (it travels the same distance), and will therefore be in phase with the signals from the others.
But if the source is off to one side, then the signal received from the near antenna will have traveled a shorter distance, and will be out of phase with the others by an amount proportional to the sine of the angle to the source.

(+1) It's interesting that it can detect the time difference for a signal traveling at the speed of light in that short of a distance! Do you know if there's also a vertical offset to detect signals from sources that are higher or lower than the F-16? Just because the nose is curved, it seems like there's an offset... but I can't tell if it's intentional.

@F16Falcon: They are probably not measuring “arrival time” with a highly accurate clock (you’d probably need dozens of GHz) but instead just detect phase difference by subtracting the signals.

As @F16Falcon said, there is no clock involved. The processor simply adds, (or subtracts), the signals to measure the phase difference between them. Knowing the frequency of the signal, and that the two signals originated at the same point and time, the phase difference can be used to calculate the difference in distance traveled. Knowing the difference in distance traveled, and the geometry of the antennas, you can calculate the arrival angle.

As to whether the system detects the vertical angle, I flew the F-4, not the F-16, so I am not sure, but my assumption would be no, the main purpose of these systems (on the F-4 anyway), was to display the relative azimuth of threats on a circular threat display. In the F-4, during the Vietnam War, this was primarily ground threats like acquisition and tracking radars, and Active/Semi-Active Surface to Air Missiles (SAMs), so the vertical angle was not that important.


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What is this hole on the F-22 Raptor?
I noticed this little hole that is right in front of the cockpit window of the F-22 Raptor. In some photos, it seems to be closed, while in other photos, it's open.
Does anyone know (or think they know) what the purpose of this hole is? Is it a ram air intake for air conditioning? Or is this classified?
Here are examples:
Closed hole:

Open hole:

source: Stack Exchange

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sort: votes


text:
Under which condition is a forward CG most critical?
This question is from CFI written exam. (6824)
“Under which condition is a forward CG most critical?”
The answer is
“Forward CG is most critical during landing. If it is too far forward, the elevators may not have enough power to get the tail down for a proper approach and flare.”
I don’t know why if CG is too forward, the elevators may be less effective. In my mind, if something has longer arm, that one becomes more effective like teeter-totter.
That would be great if someone could help me!

One intuitive way to think about this is that the pitching motion of a rigid body occurs at its CG. At forward CG, the elevator, which pitches the aircraft up, indeed has a longer moment arm. On the other hand, however, the wing lift vector, which tends to pitch the aircraft down, also has a longer moment arm. The proportion of change of the wing lift moment arm is quite a bit more than that of the elevator, for the same change in CG. In the end, the wing lift, which is also quite a bit larger, wins this race. Hence, forward CG is more critical for maneuvering.
Strange that it says landing, which I assume is the flare portion, is the most critical condition. I would've thought takeoff rotation would be equally bad, especially if you have a mistrim.

I guess the latter comes from the implicit assumption that the landing flaps configuration creates more pitch-down moment. In practice, this is true for most aircraft.

@zeus Very true, but you'd think that the pilot would've trimmed the aircraft on approach prior to flare.

By too far do you mean outside the fwd limit? If yes then is a question of the elevator having insufficient 'arm' to counter the increased 'arm' of the (too fwd)CG.
If the CG is within limits or even 'on' the fwd limit then the airplane should have no problems with elevator effectiveness. Airlines usually add a bit onto the manufacturer's limit as the manufacturer limits are based on static conditions (no movement of load) but airlines usually have people and equipment(galley carts) going thru the cabin in flight so the airlines will add some buffer.

The elevator is producing downward lift.  It is you pushing down at one end of the teeter totter.  Your kid is sitting on the other end of the teeter totter, and the teeter totter's center of gravity is somewhere between the pivot and your kid.  If you stop pushing down, he drops.  If your kid moves farther out, say by leaning back, you may not have the strength to keep pushing down and down he goes.  Having the CG too far forward is like your kid moved farther out than you can handle.
This is a problem when the horizontal tail is working at the limit of its strength you might say, at low speed and with the elevator at maximum deflection, without any slipstream blowing on it.  When the CG is too far forward, it can't push down hard enough to hold the nose up at the normal landing speed, and has to go faster to do so.

Your teeter totter analogy is flawed. A plane doesn’t have a fulcrum. Rotational motion is about the CG. So forward CG makes a long moment arm.

Obviously it's an imperfect analogy, it being in fluid.  But the neutral point is effectively the fulcrum for the purpose of thinking about the moments and forces involved, and the analogy does the job for someone trying to mentally imagine what is happening.

@TomMcW this center of gravity thing will earn you points here, but in reality putting the fulcrum at the center of lift makes the static stability model work quite well.  The CG torque arm is constant, the tail downforce varies with airspeed.  As the plane slows down to land, aerodynamic down force can reach a limit if CG is too far forward.  It is indeed a teeter totter, with weight on one end and and elevator trim blowing in the wind on the other.

@RobertDiGiovanni I see what you guys are saying. Makes sense.

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Difference between Assessment and Critique?
I was reading Aviation Instructor Handbook. I don't know the difference between assessment and critique. That would be great if someone could explain about it! Thank you!
In my understanding, assessment is just comparing student's performance to established standards without saying it was good or bad. And, critique is more like telling the way or process student performs was good or poor without comparing to the standards. But, I'm not completely sure.

My understanding of the difference between assessing and critiquing is this.
Assessing or assessment involves grading a subjects performance or ability against a given standard or ideal. This can involve a letter or numeric grading, or a simple pass/fail grade. When grading against an ideal subject or situation, absent of an accepted standard, can be rather subjective.
Critiquing or a critique is a judgement of the way a subject performs. It is not meant as a way to judge the performance. Rather, it is meant to provide feedback to the subject regardless of the grade against the standard in order for them to improve. This is much like coaching. You would coach both your worst and your best performer for them both to improve. Even if their performance warranted a passing grade.

That's great explanation!! Assessment involves grading and critique is more like providing feedback. It helps me a lot!! Thank you so much!

Welcome to the Aviation forums.  Once you become a CFI, you join a unique group of people.  It isn't easy but well worth the effort.
I have perused the Aviation Instructors Handbook Chapter 6.  From my reading and what I do with my students I would consider an assessment a formal evaluation of the students performance.  A critique would be an informal evaluation and is usually part of the debrief after the flight.
I spend considerable time briefing the students on what the flight lesson is going to entail and the performance standards I am using, answer questions from study assignments and talk general pilot knowledge and things they need to know to become a great pilot and also to pass the oral test.
Once the flight is over, I spend time talking with the student on their performance.  It is a one-to-one conversation where we both determine where the student is at and decide what the next lesson is going to be.  This would be a critique.
I personally start out asking the students how they felt the lesson went for them... where things went well and where things need extra attention next time.  I then start my critique where I describe what went well and what went not so well.  At the conclusion we discuss what the next study assignment is going to be and the next flight training session is going to entail.
After the student leaves, I will sit down and formally document in the students training folder the items that we trained and the grades they received.  This would be the assessment.
If I were to sum up this answer in a sentence. Critiques are informal discussions on performance and assessments are formal documentation of the performance.

Thank you for explaining!! I really appreciate you gave me a real life example. It much easier to understand!!


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Why don't all cylinders have priming lines?
Questions about the primer for carburetor engines.
Why does the primer only spray fuel to three (sometimes just one) of four cylinders. (Like Piper Cherokee or Seminole)
And is it true that priming engine during engine start (cranking engine) may cause engine fire?
That would be great if you could answer those questions! Thank you!

The airplane maker will not normally install any more primer lines than necessary. In warm environments it's not usually necessary to prime more than one cylinder, so you will see airplanes operated in the southern US with single primer lines more often than in the northern US or Canada.  My old '68 Cardinal only had a single primer port because it had been imported from the US that way (I was in Toronto at the time), and it was murder to get it started even in moderately cold weather without preheat. I had primers run to all 4 cylinders by my mechanic.
Also, you will often see one of the threaded holes at the intake port on a cylinder being used as a tap-off for a manifold pressure gauge, another reason for stopping at 3 lines.
When priming, the objective is to get a good coating of raw fuel in the intake pipes close to the port, that will take 5 or 10 seconds to fully evaporate after starting, to provide that temporary extra-rich mixture.  But not too much.
Over-priming can start a fire when so much gas is squirted in it starts to collect in the intake pipes and drain down into the airbox.  A backfire into the intake system during starting, because an intake valve doesn't quite seal, can ignite the fuel in the airbox, and potentially fuel that is dripping into the cowling.
That's why, when cranking and you hear a "fump!" sound under the cowling, keep cranking!  You need to try to draw any ignited raw fuel back into the intake.  Only stop cranking if you start to see smoke gushing out, and then it's time to leave and tell the owner he can have his plane back (or try to fight the fire if you want).
It's when you start to smell gasoline that you know you've over done it.  Best to stop and wait a while for all the gas to evaporate.
A worse habit is throttle pumping to spray fuel from the carb's accelerator pump into the intake.  You might do it when you start a warm engine; it's not necessary to prime with the primer and little shot of throttle while cranking is enough.
But it's critical to only pump the throttle during cranking. If you pump it while things are stopped, gasoline runs straight down into the airbox immediately.  Probably most cowl fires are from people pumping throttle several times, waiting a few seconds, then starting, then it's "Fump!".... "do you smell something?".

Thank you for explaining and sharing your experience!

On a large radial engine, priming may be done without any dedicated line to a particular cylinder.  It used to be standard practice in the winter time to flood the supercharger while cranking until fuel ran out of the drain, with a five gallon bucket below to catch the fuel.  Apply spark, begin advancing the mixture and cracking the throttle; the priming was simply raw fuel dumped into the supercharger.
Fuel doesn't need to flow to every cylinder to prime, as the fuel source is the carburetor.  This is true whether it's a small horizontally opposed engine, or a large radial.  The point of priming is to get the engine to start picking up the load of the starter and to be self-sustaining.  Every cylinder will come to life on its own; regardless of the engine, mixture and fuel and ignition is different in every cylinder.  Not all will fire off at the same time.
Priming every cylinder can result in a fire.  Typical primers in small engines in light piston singles are often plunger type primers that move a very small amount of fuel.  That fuel is more useful and effective if directed to one or two cylinders, than spread among multiple cylinders.  Priming all cylinders with such a small amount of fuel might result in multiple plungers of fuel being required, and less precise application of the fuel (and the possibility of overpriming.
It should also be noted that under certain circumstances, an unlocked primer can result in a rich fuel situation and spark plug fouling (by drawing fuel through the primer), whereas a failure in a primer line can result in a lean cylinder operation, or a fire.  It makes sense to limit the number of primer lines to those necessary to assist engine start.  Some cylinders during start operate more lean than others due to intake design, distance from carburetor, etc.
In engines that are fuel injected, each cylinder is primed, in some cases, using a boost pump and normal fuel flow, and in others through dedicated priming lines to one or two cylinders only.
In a previously reply, someone mentioned pumping the throttle, which on certain installations, invokes an acceleration pump.  The acceleration pump adds additional fuel, usually as a spray, during throttle advancement, helping to reduce engine stumble, or a lean mixture.  Some times this accelerator pump is called for as part of the starting procedure, but in many cases, it's used incorrectly as a means of "priming the engine."  It's a good example of the need to know one's aircraft, systems, and procedures.  What's true of one aircraft model or engine installation is not necessarily true of another, even when the same engines are used.

In addition to John K, it only takes one or two cylinders to fire before the engine will start. Just like when pull starting a lawn mower, once the cylinder fires once it will almost always start, similar principle here, while priming all cylinders would not hinder starting, if it only takes one of them to fire it is pointless to prime all of them.

"...once the cylinder fires once it will almost always start..."  You really think so?  Not my experience, and part of why I have an electric lawnmower now :-)

I know what you mean, lawnmower engines can be hard to start, but they (usually and understandably) aren't maintained to the same standard as plane engines. Often using lower quality fuel that has been sitting for months with bits of grass in them, blocked air filters, fouled plugs due to tilting so oil goes into the intake etc. Electric mowers are way easier definitely, we need electric planes @jamesqf but I haven't found an extension lead long enough and batteries aren't there yet.


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How much maintenance time did it take to make an F4U Corsair ready for another flight?
A coworker I worked alongside once told me that during his time in the Navy, he was responsible for taking care of maintenance on F-22s. He stated that every F-22 required 10 hours of maintenance for every hour of flight.
I am curious how this level of maintenance stacked up against older less-modern aircraft. For the sake of narrowing it down, let's take the F4U Corsair as an example. Assuming a routine flight (training or simply air-patrol), what was the amount of time that would be required to maintain the aircraft on the ground to keep it safe for its next flight? 1 hour? 2 Hours?

Although that number may be correct, it is highly unlikely that your friend worked on F-22s if he was in the Navy.  Raptors are an Air Force plane.

Figures like this are a bit of an awkward 'time accounting' issue, and answers would ideally take care to include what hours they're including. [ie, 'total support hours' can include the cook's time for meals for all the crew involved, but is not 'maintenance time', while the time spent by crew changing out and loading ammo belts gets into a bit more of a fuzzy zone.]

@MichaelHall maybe the friend said Air Force and the OP just mixed them up. Or, maybe OP couldn't remember the specific airplane so just said the one they could think of.

Yes, most likely...  I just wanted to mention it to prevent anyone from being confused.

The model does matter a lot, though. Relative time spent on maintenance does vary quite a bit, even among modern planes.

"10 hours of maintenance for every hour of flight." does not mean it takes ten hours to get the plane ready for the next flight, or even that it takes ten people an hour to get it ready for the next flight. It might take much less than that to turnround for the next flight, but requires hundreds of hours maintenence every ten or twenty flights.

Far more than that. Try 50 maintenance hours per flight hour.

actually finding a reliable source on-line has proven to be a bit difficult. RNZAF, pacific maintenance 58 man hours per flying hour. NZ based (training) F4u 50.5 man hours per flying hour. P51s NZ based (conversion and training) 36 man hours per flight hour.

Piston engines (esp. WW2-era high-performance fighter engines) are very maintenance-intensive compared to jets.
Here's a comparison of various military aircraft types:
Saab Draken.- 50 to 1
Eurofighter....- 9 to 1
F-14............. - 24 to 1
F-18E/F........- 6 to 1
F-18E/F........- 15 to 1 (different source)
Saab Gripen..- 10 to 1
C-17.............- 20 to 1
F-15A/B........- 32.3
F-15C/D........- 22.1
F-16A...........- 19.2
F-117...........- 150
F-117...........- 45 (after improvements, post 1989)
CH-46E........- 19.6 in 1995 GlobalSecurity.org
CH-46E........- 27.2 in 2000
CH-53D........- 24.8 in 1995
CH-53D........- 27.9 in 2000
F-20.............- 5.6
A-6E............- 51.9
F/A-18C.......- 19.1
B-2..............- 124
and you can see modern fighters require far less maintenance hours/flight hour due to several factors:

improved systems that require less frequent maintenance
design improvements to make maintenance take less time (better access, more line-replaceable units)

I looked at your first link and didn't find the reference 50 maintenance hours per flight hour. Is the link correct? Also, I'm not sure a discussion forum represents an authoritative source.

There were 3 figures on that page, I rounded off the average.

Could you check the link? I don't see any figures at all...

The quote at the start of my answer is copied directly from that page.

Ok, I found it. It was in a section that had to be expanded.

Possibly worth clarifying that these are maintenance man-hours rather than clock hours; it's not clear which figure OP is interested in.

OP said "amount of time that would be required to maintain the aircraft on the ground", so sounds more like wall-clock time. Thus, depending on the aircraft and specific tasks needed, you could throw more people at it to complete checks faster.

This is an excellent answer and nearly completely answers my question. I realize now that the question lacked clarity. I will update the question appropriately.


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What are these panels underneath the wing root of a A380?
What are these open panels underneath the wing root of a A380 (right above the person standing under the aircraft)? Are they ram air exhausts of the air conditioning packs?

If nothing else, the included picture lends an awe to the size of the A380 compared to the crew person underneath.

They are indeed the Ram Air Outlet Doors.

(source, showing Ram Air Inlet (RAI) and Ram Air Outlets (RAO))
From the A380 FCOM (21 - Air Conditioning):

PACK DESCRIPTION
  The hot bleed air flows into each pack, via the two pack valves, then enters the heat exchanger. This
  heat exchanger precools the air using external air. This external air enters through a ram air inlet door,
  and is then discharged overboard through two ram air outlet doors.

The reason they are located in the wing root is that the entire packs are in the wings. From this article:

The A380's wings are big enough that they can hold the plane's air conditioning packs. That, says Airbus, is an advantage over most other large planes because the packs don't have to be stored in the A380's belly fairing. That, in turn, means the plane's fuselage is more streamlined than it would otherwise be, reducing its drag.

@Intellex it's ram as in ramming into something - the oncoming air rams into the inlet.

@Intellex There's something called a ram air turbine, which is an emergency source of power that extracts energy from oncoming air. However, according to the picture in this answer I think this is something different; this is just a source of cold air for the air conditioning system to dissipate heat into.

@Intellex The ram air is called like that because it is not sucked into the aircraft by a fan or something similar, but is instead created by flying through the air fast enough to scoop it up (that is why the inlets are shaped like that). The RAT (Ram Air Turbine) is a propeller that can drop out of the fuselage in an emergency to generate electricity and hydraulic pressure. It is powered by ram air, hence the name, but is unrelated to the ram air for the air conditioning.


text:
Is this a very sloppy holding pattern or something else?
This scheduled Belavia service to Barcelona appears to be in a very sloppy holding pattern where they aren't correcting for wind at all. Is it normal for a passenger jet to fly like this?

It does indeed look like they are not correcting for wind. The current wind over Belarus at 10km altitude looks like this:

(screenshot from windy.com)
That is consistent with the direction in which they are drifting. Such a flight path is not a normal holding pattern, which is based on a holding fix. While wind might push the aircraft somewhat off the nominal racetrack pattern, they would at least regularly overfly this fix (although modern RNAV systems are pretty good at compensating for wind).
I can only speculate on why they are flying like this. Most likely they are not holding at a specified fix. They might have been instructed to hold at current position by ATC, probably while they figure out if they are still allowed to fly into the EU, after the European Council has called for a ban:

The European Council:

[...] calls on the Council to adopt the necessary measures to ban overflight of EU airspace by Belarusian airlines and prevent access to EU airports of flights operated by such airlines;

(europa.eu)

Update: It seems they are returning now:

(flightradar24.com)

@ymb1 Never heard orbit left before, but that sounds like what they're doing. I'm not super familiar with the E-Jets, but as far as I know they don't have an attitude hold mode. There is a TCS (toch control steering) button on the yoke, but according to the Auto Flight System description that is only for overwriting pitch. Lateral control resumes when releasing the button. No idea what modes they used.

The E-Jet default lateral mode is "roll".  It's equivalent to attitude hold in some situations.


text:
Is Autopilot NAV setting useful?
In flight simulator, using the NAV setting directs the Autopilot to follow the FMS' pre-setup flight plan and will navigate the aircraft through each of the configured waypoints.
In real life, however, it seems almost a guarantee that ATC will provide some heading which is not necessarily the most direct route, ie. what your flight plan had configured. ATC will request you turn right or left somewhere around the waypoint you expected, but not where you or the NAV system would have turned.
Even in the simulator, if you use the built-in ATC, it will give headings that are not what the flight plan had expected... making the NAV button not very useful except when flying VFR without following.
It seems the autopilot HDG feature is used more often. Is this true in real life as well?

Why not just adjust the FMS to reflect what ATC provides for instructions? The FMS is easily reprogrammed in flight...

@RonBeyer My terminology is probably wrong, so please excuse me. When I fly in the simulator, I have my waypoints setup, but ATC navigates me usually miles away from the waypoint, or past the waypoint, before issuing the next heading. If you're suggesting to adjust each waypoint to a simple heading, I'm not sure how that would work? It usually tells you estimated time and miles left until the waypoint is reached, but you don't know what the waypoint is if it's just a heading... no?

I'm not sure your simulator is an accurate representation of the real-world. Usually IFR flight plans are "cleared direct" or "as filed", and are relatively rarely amended in flight. ATC shouldn't be calling your every turn, that is why you have flight plans. The only time you may get routed around is coming into a busy field for spacing, but even then if you are on an IFR flight plan you should be spaced in long before you get there.

@RonBeyer Perhaps I'm "doing it wrong" then. Typically I take off after getting clearance, and get transferred to Center. Then I fly whatever heading they told me at whatever altitude they want, until I get the next heading, etc. When I watch my map, I typically will be close to, but not on the purple line the FMS has setup between waypoints. I usually get my next heading somewhere around my expected waypoint, but not exactly on it. Sometimes I'm miles to the right, left, or beyond it before I get the next heading. I'm flying prepar3d btw, if it matters.

@mins I typically have it set to Clear Skies and Calm Weather. There is some wind, but not a lot.

So to answer your question (in the title): NAV is useful to compensate for wind drift, a drift not corrected by the HDG mode.

@mins Maybe this is where I was getting confused. So if ATC says "Turn right heading 175" but my flight plan thinks I should turn right 185, which do I follow?

@SnakeDoc: If you want to discuss, then you must use the chat feature.

In flight simulator, using the NAV setting directs the Autopilot to follow the FMS' pre-setup flight plan and will navigate the aircraft through each of the configured waypoints.

No. The NAV mode follows VOR radial. The FMS might provide "virtual vor" and use NAV mode too, but usually there is a separate LNAV mode for FMS.

In real life, however, it seems almost a guarantee that ATC will provide some heading which is not necessarily the most direct route, ie. what your flight plan had configured. ATC will request you turn right or left somewhere around the waypoint you expected, but not where you or the NAV system would have turned.

No.

In real life, most of the time you follow the flight plan. And even if the ATC wants you to fly other route, they will tell you new set of routes or fixes to use and you punch them in the FMS, so you still fly LNAV.
Exception is approach where it is common that ATC will have you fly downwind (opposite direction than the runway) and tell you to turn base and intercept the final approach, so there they will give you heading (and you use HDG mode on the A/P). But that is once during the flight. Sometimes also once on departure, but that's usually it.
The ATC can also tell you to follow some radial of some VOR and that's where you use the NAV mode proper, not the LNAV mode used for following FMS.
Your flight plan is usually not direct, but follows the defined airways.

Even in the simulator, if you use the built-in ATC, it will give headings that are not what the flight plan had expected... making the NAV button not very useful except when flying VFR without following.

I am not sure how realistic the simulator ATC is and would't expect much of it. You'd get a better result in something like IVAO where the controllers are played by real people.

It seems the autopilot HDG feature is used more often. Is this true in real life as well?

The HDG feature is used when the ATC vectors you around. It usually happens on busy airports on approach and on really busy airports on departure, but enroute it is rare.
The LNAV feature is used most of the time. The NAV feature is indeed rare, because most of the time you use FMS, not a raw VOR.

There are essentially two scenarios on departure: an initial vector, or flying the departure procedure track immediately "off the ground."
In the former case, the instructions might be along the lines of, "fly heading 120, expect vectors to JEBBB" or "... to join the WHOZT5 departure."  In that case, shortly after takeoff, the pilot would select Heading mode and fly the specified heading.  At some point after that, ATC would issue a clearance to proceed direct to a fix, and then the filed route would be flown from that point on.  So upon receiving this clearance, the pilot would proceed direct to the given waypoint by engaging NAV (or, given modern nomenclature, LNAV).
In the other case, the first leg of the departure corresponds to the "straight ahead" track of the departure runway, and LNAV is activated immediately after departure, and the aircraft will fly the magenta line as published.  So in this case, Heading mode isn't used, unless ATC needs to vector the aircraft off of the published track.  In that case, they can either issue a vector, or they can clear the aircraft to a later point in the procedure or along the route.
In modern ATC, it is very uncommon for an aircraft to be getting vectors enroute, simply because it is more workload for the controller with no benefit.  Once you're away from the terminal area, they clear you on whatever route you've filed (or been assigned), and they don't have to do any more navigating for you.  If they need to turn you off course for traffic, they will, but that's the exception, not the norm.

Additionally, more and more aircraft and ATC facilities support CPDLC (Controller - Pilot Data Link Communications).  When enroute, ATC can data link an amended clearance.  When the pilot accepts the clearance, the FMS updates the flight plan automatically.

On FSX you have to change the NAV/GPS toggle switch to GPS to follow the preplanned route which is shown in the FMS display. Once you reach your designated airport the ATC will give you vectors to intercept the ILS. At this stage you need to enter the ILS frequency into the NAV1 and switch the toggle switch to NAV. The autopilot will then follow the ILS. Not sure how realistic this is with real life flying!

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text:
Why does Airbus suppress stall warnings in certain situations?
I was reading about Air France 447 and came across the line:

The stall warnings stopped, as all airspeed indications were now considered invalid by the aircraft's computer due to the high angle of attack.

In short, due to pilot error, the aircraft (A330) reached a 40 degree angle of attack while under Alternative Law (due to icing conditions) and stalled at 52 kts. Further confusion came from the stall warning suppressing itself after some period of time.

Roughly 20 seconds later, at 02:12 UTC, the pilot decreased the aircraft's pitch slightly, airspeed indications became valid and the stall warning sounded again and sounded intermittently for the remaining duration of the flight, but stopped when the pilot increased the aircraft's nose-up pitch.

It would seem, if the aircraft was stalled, and the computers knew the angle of attack was still far greater than normal, that it's most reasonable to assume the aircraft would still be in a stall even after other sensor data became unreliable. Also, if no airspeed sensors are reading valid data... seems it's most reasonable to assume the aircraft is in a stall... or on the ground (but wheel load sensors can corroborate when that's the case) - not just give up and assume everything is fine.
It seems to me, that perhaps this stall warning is at least partly at fault for this accident.
Why did Airbus design the stall warning system to suppress warnings in this situation?

AF447 didn't stall at 52 KIAS - the 52-KIAS reading was erroneous, due to the blocked pitot tubes (as evidenced by the fact that, 29 seconds later, the airspeed reading jumped back up to 223 KIAS, while the aircraft was still climbing).  It stalled later, after the airspeed indications had become valid again.

Stall warning was inhibited below 60 knots airspeed, in order to eliminate nuisance warnings during taxi and other situations. It is well below the stall speed of an A330 in cruise configuration:

landing speed with flaps extended is in order of 135 knots;
stall speed in landing configuration would be in order of magnitude of 120 knots;
stall speed in cruise configuration way above that.

It was indeed a very tragic circumstance, one of the factors preventing the flight crew from recovering from their situation. The solution however, perhaps in addition to enabling stall warnings for very low speeds in cruise configuration, is to train flight crews in recovering from a fully developed stall. During recovery, the load factor must remain under 2.5 g, the structural limit for an airliner.
This is now mandated by regulation authorities, and the first systems have been certified for training use at airlines. FAA has published 14 CFR part 60 Change 2 for upset recovery training. Alaska Airlines had the first Part 121 simulator certified for Full Stall Training under Part 60 Change 2, in April 2016. The simulator is a B737-800.

Is this official/authoritative reasoning? I ask, because it doesn't make much sense. If it's a nuisance, why not have a button to silence it, so pilot knows the stall didn't go away on it's own. Or simply have wheel loading sensors to determine if the aircraft is on the ground or not (inhibiting the warning when on the ground only). The flight crew didn't realize they were developing a full stall partly because the stall indicator silenced itself when nosing up (the opposite of what was expected). A full stall will be at low airspeed, which is precisely when you need the warning.

@SnakeDoc because encouraging the pilots to cancel frequent warnings/alerts can cause them to miss something important.

@fooot I would hope stall warnings aren't frequent when at cruise (at least when the computers think the aircraft is at cruise).

The backup speed tape now provides direct AoA indication. In a fully developed stall from cruise altitude at speeds lower than 60 knots, you need way more than a beeping horn. But yeah you do have a point for the cruise configuration.

@Koyovis Part of the reason a full stall was developed was due to non-linked (physical or otherwise) flight sticks. One pilot was pushing slightly down (correct), and the other was pulling hard back (incorrect), causing the plane to climb until a full stall was developed (they had no idea they were giving conflicting inputs). The pilot continued holding back on the stick since the stall warning went away, and they had no airspeed indicator to make them believe they were in a stall anymore. Several things compounded, but seems this indicator could have helped. Just my opinion :)

@Koyovis Can you cite something official for your answer so I can accept it?

Added reference to changed FAA regulation, and a link to the first solution implemented.

@Snakedoc yes agreed on the stall warning and the tragic circumstances. There is a question about adding the stick inputs on this site.

@Koyovis Thank you! I'll do some more reading up on the stick inputs... that still boggles my mind. I might just not be an Airbus fan ;-P

@Sankedoc it is my firm belief that the sticks shoukd be coupled. Other than that I do appreciate the design philosophy of Airbus, their safety numbers are excellent. As are those of Boeing.

@SnakeDoc The airspeed indicators were actually working fine after the initial icing had cleared, the pilots just didn't believe them afterwards. I too think the sticks should be coupled but that's not a perfect solution - an ATR recently suffered severe damage after the control inputs differed (https://www.atsb.gov.au/publications/investigation_reports/2014/aair/ao-2014-032/). The better solution is better crew awareness, procedures and training.

@Ben agreed. Proper procedure is for one pilot flying.

How do two pilots, in the same cockpit, not notice that (a) they're both giving control input and (b) that they're giving different control inputs? Man, everything about how they crashed this plane is crazy.

@IanKemp: Possibly because, in the A330, control is via sidesticks on the window sides of the pilots' seats, making it a lot harder to notice what control inputs your copilot is making than it would be on a plane with a conventional yoke (like, for instance, an A300, or any Boeing airliner ever).

The stall warning needs to be an immediate attention-getting alarm that you react to promptly and accurately.  If you routinely hear it on landing roll-out or during taxi, and 9,999 times out of 10,000 your reaction has been to cancel it, then on that one time (or less) in a career that you're hearing it for real, there would be a real risk of cancelling it instead of reacting to it.  Thus, the need to inhibit nuisance alarms.
The problem on AF447 was two-fold: the defective pitot tube heating setup, and the gross mishandling of the aircraft by the FO.  If the pitot tube heat hadn't failed, no accident.  If the FO hadn't made control inputs that run counter to every training, every instinct, every habit of flying pilots throughout the world  for the last 100+ years, no accident.  What that pilot did was so far outside of what's expected that no amount of "normal" systems or procedures was going to do very well dealing with it.  You simply don't train for what to do or what to look for in a case where the other pilot does something utterly irrational that defies all common sense and training.
There are things that Airbus aircraft could do differently so that the other pilot knows what sorts of inputs his partner is making, and there are always things that can be done differently in fly-by-wire and warning systems.  But at some point, you have to make assumptions that the pilots have been trained and that they won't do things entirely opposite to that training -- especially when you're already in a degraded state without full protections and full air data inputs available.
Enabling nuisance stall warnings & building a habit pattern of cancelling them isn't going to make things better.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Do you pay to Touch-and-Go?
I understand you pay to land at an airfield, but do you pay to Touch-and-Go?
Pilots will often practice many Touch-and-Go's at an airfield, are you billed for each one (assuming you pay something to use the airfield's resources for the Touch-and-Go procedure).
How are you charged if you don't do a full-stop at the field (practicing at another airfield different from your home base)?

Which country are you asking about?

@slookabill I'm most interested in US, but if it differs elsewhere, that would be interesting to know as well.

Very few airfields charge for landing, essentially just major commercial ones that don't want private traffic.  Some will charge for overnight tiedowns, but most smaller ones are "free" in the sense that roads are free - that is, you're paying through gas taxes &c.

@jamesqf Is that true at private airfields (ones that allow GA but are not owned by the city, etc)? Private roads/bridges have tolls, so I'd assume it's the same, no?

Except for the largest airports, most airports in the US do not charge a landing fee. Santa Monica (KSMO) wants to shut down the airport and they currently charge small GA aircraft $7 for each landing or touch and go—even the ones based there. If you stop at an FBO, to drop off passengers or take a break, the FBO will usually charge you. Many airports have free parking at the restaurant or near the self-serve fuel pumps.

@SnakeDoc: AFAIK, most private fields are just that, private, so you should have prior permission from the owner before landing.  I suppose if they're associated with a resort or something, they might charge, but I've never encountered one myself.  But I do most of my flying in the western US, and to strips that are either dirt or if paved, have minimal facilities.  They seem to be owned by county, state, or Forest Service/BLM.

It really depends.  15 years ago at BWI there was no fee for touch and goes, even for aircraft that were not based there.  I'm not sure what their policy is currently.

It varies.  Some airports charge by landing, others by operation (a series of landings if training).  Some charge through the FBO, who may waive the fee with fuel purchase.  Expect that multiple landings at BOS or JFK will result in multiple fees, often billed to the registered owner.  It was a while ago, but I did a series (about 12) of landings at BOS one night, and the owner/operator paid 25 dollars each. Someone told me recently that the fee was more like $65 now for a Cessna P210.
To be clear, call the airport and ask them, or check their web page, which may have their charges and rules on it.  And/or check with an FBO or two at the field.

Its address more or less in this question but they will bill you by tail number (to the owner operator on file). Generally speaking for touch-and-gos the landing fee is only applied once a day so you can do as many as you like and only pay the fee once (in my experience) as an example you can find the fee structure and payment info for KPNE (where I fly out of sometimes) here.

Wow, $5 is a lot less than I expected. The landing fees for GA are probably the cheapest part.

I don't completely understand your comments about KPNE. In the other question you mentioned a $5 landing fee paid at the FBO, which sounds normal enough. But your answer here makes it sounds like they charge you $5 just to do touch and goes, even if you never do a full stop or use the ramp/FBO. Is that correct?

I have always flown out of there and paid at the FBO but I belive if you do Touch-and-gos they send a bill to the aircraft owner/operator after the fact. The regulation does not specify full stop landings vs touch-and-go for the billing. At the other FBO/Flight schools I have rented from at uncontrolled fields I have seen them receive bills for such operations.


text:
What type of display is used for cockpit displays?
In "glass cockpit" aircraft, what type of display is used for the PFD/MFD system?
Are they normal LCD screens, or are they "special" in some way (temperature tolerance, refresh rates, shatter resistance, etc...)?
Typical PFD/MFD:

Typical raw panel LCD screen:

The first ones were CRT and then switched to LCD. Of course they have more requirements for reliability, temperature, vibration, etc. than the typical monitor that sits on a desk or even in a laptop.

I do wish we had more resolution available for the G1000. In most GA aircraft, the G1000 is 1024x768. What is this, 2003?

Modern glass cockpits use LCD screens specially designed to be visible in bright sunlight.  Earlier units used cathode ray tubes.
Both the Boeing PFD screen and the Garmin G1000 PFD shown above use LCD screens.

Any references for this?

The original 747 had CRT displays.  Boeing shifted to LCDs in the late 90's when CRTs became non-procurable.  They actually had to get a cert to allow for flight decks with a mix of LCDs and CRTs.  That allowed airlines to swap out just one failed CRT with an LCD.  That avoided having to replace all displays when one failed.

The first PFD/MFD used CRT and as technology progressed, PFD/MFD was now developed and showed as LCD. CRT generates a lot of heat and consumes a huge amount of voltage (up to 50,000V) while LCD takes maximum 5V, which means less heat generated.
In addition, the development of LCD also gives us a better resolution compared to CRT and literally has no glare effect on the screen. You can see more pros and cons comparison between these 2 in the link below:
http://bootstrike.com/Articles/LCDvsCRT/

Voltage and heat generation are not related (or only tangentially due to conversion losses).

Power is calculated by P = V^2/R = I^2R = VI. Heat dissipation is calculated by H = P*t as t is the time in second!

Yes. And as such, you will find that high voltage devices generally use very little current at that high voltage, but since the useful power output is also P=U*I, the result is the same.

Ah ok. That makes sense. Thanks for your explanation!


text:
Has a life raft ever been successfully deployed in case of an accident?
Has a life rift ever been successfully deployed in the event of an air accident?
By successfully I mean removed from the aircraft, placed on the water, inflated and used by passengers/crew as a life raft.

This question is too broad. The answer is yes, many, many, many times. You need to narrow it down in scope to get a reasonable answer.

It's really not all that broad and it is singularly answerable. Might not be the answer the OP is after, but it's a simple, concrete answer to the question.

Actually I should have limited it to commercial airliners. Pants.

Voted to close, I'll try again, but it's frustrating that there is no way to fix it and keep the existing answers that are appreciated.

Sure.  For example, Eddie Rickenbacker and 6 other people spent 3 weeks adrift aboard life rafts after their B-17 ditched in WW2.
Read more -- https://www.historynet.com/eddie-rickenbacker-and-six-other-people-survive-a-b-17-crash-and-three-weeks-lost-in-the-pacific-ocean.htm

I'm not sure if a WW2 bomber qualify as commercial

@QuentinH that qualification was edited in after this answer. Hate it when an edit invalidates an answer.

@Jamiec nicely spotted, I should have checked. Maybe the other guys did order some US "carpets" with next-day delivery though... that would make the answer valid.

Btw the linked article could be used as the basis for other questions.  Specifically-- . "In the end, however, all Y could provide was a compass course reading, which was worthless since that did not tell the crew whether they were flying toward or away from their destination. Without a bearing the pilot did not know in which direction to fly."  -- How is this plausible?  The author would have us believe "island Y" could tell the B-17 which direction it was flying but could not provide a bearing?  This makes no sense.  Actually, it's so nonsensical that it's probably not a good subject for a q

"An hour before the estimated arrival time, Captain Cherry throttled back, slowly descended to about 1,000 feet and began looking for Canton Island."  -- this makes no sense either, unless there was an overcast above this level -- you've been flying over  the ocean for almost 2000 miles and you don't know exactly where you are so your strategy is to descend  to a thousand feet, where your field of view will be greatly limited-- a whole hour before your ETA?  Interesting.  I don't think the author was a pilot.

It would be interesting to find a more authoritative/ plausible description of the flight.

US Airways Flight 1549 ditched in the Hudson river after a multi-engine bird strike on January 15, 2009.
According to these pictures, they did deploy the emergency slides which were eventually detached and used as emergency rafts:

Emergency slides in airliners are actual life rafts. They are designed for that and often include survival kits and canopies:

I agree with @ymb, the criteria (from the start) was that the life rafts be deployed. Make-shift rafts make out of slides don't count I'm afraid.

Slides are NOT make-shift rafts. They are designed to be rafts once everyone is out of the aircraft.

Some even have sun canopies https://i.pinimg.com/originals/ad/08/40/ad0840f0f4e3ad8640d0e7b38227ff8f.jpg


text:
Has a life raft ever been successfully deployed on a modern commercial flight?
Has a life rift ever been successfully deployed in the event of an air accident involving a commercial aircraft?
For the purposes of this question a "life raft" is an inflatable device designed specifically and only to be used as a life raft and normally stored inside the aircraft, not some multi-purpose or makeshift device.
Criteria for inclusion:

A commercial jet flight after 1945
Carrying paying passengers
Minimum aircraft capacity 50 people, although fewer may have been on-board at the time
Raft stored inside the aircraft prior to deployment
Raft designed for this purpose, i.e. not just something a passenger was randomly carrying
The raft actually worked as intended, i.e. people were able to float on the water in it and not drown

In short I'm asking about the rafts often seen stored away on commercial flights. The raft may have been used on rivers or the ocean.

(Image source) A Boeing 737 ceiling compartment where such raft can be stored.

https://www.huffpost.com/entry/mircale-water-landings-be_b_11969142

Are you excluding the inflatable emergency exit slides that deploy from doorways and which are explicitly designed to detach and function as life-rafts?

@RedGrittyBrick yes

Just to save other folks some time:  the rafts used during the "Miracle on the Hudson" appear to have been the inflatable emergency exit slides.

And those do not count??

Is this question inspired by https://aviation.stackexchange.com/questions/65583 ? What's the motivation -- are you wondering why it is considered worthwhile to carry a raft in a compartment such as the one shown in the photo, rather than relying on the inflatable exit slides?

For a historical example:
Japan Airlines Flight 2
On 22 November 1968, a DC-8 flying from Tokyo-Haneda to San Francisco accidentally undershot the runway at its destination by quite a bit and ended up in San Francisco Bay.

(Image originally by the United States Coast Guard, via the San Francisco Chronicle, via AlexHorovitz at Wikipedia, via Sealle at Wikimedia Commons, cropped by Josve05a at Wikimedia Commons.)
The 107 passengers and crew on board, none of whom were injured, evacuated the aircraft into five of the aircraft's seven liferafts:

Two liferafts were stowed in ceiling compartments over the aisle adjacent to rows 1 and 2.
[...]
Five 25-man liferafts were stowed in ceiling compartments in the aft passenger compartment. Three of these were in the area of the over-wing exits over the aisle seats at rows 12 and 14 and two in tandem were over the aisle at row 31, the last row of seats, and just aft of this row.  [Page 22 of the report, numbered as page 20.]
The two forward stowed liferafts were removed from their compartments. One was launched at the main door and the other was launched through the forward service door.
Two of the four rafts stowed in the over-wing area were utilized. One was launched from each wing. One of the rafts stowed in the aft portion of the fuselage was carried forward and launched over the right wing. All of the wing-launched rafts were deployed from the leading edge of the wing.
Although some of the tourist-class passengers evacuated from the forward doors, generally the first- class entered the two forward rafts, while the tourist passengers entered the raft at the left wing and one of the rafts at the right wing. The remaining raft on the right wing was occupied by the captain and JAL employees.
From the passenger and crew statements, it was estimated that 29 passengers (no crewmembers) evacuated through the forward left door; 16 persons, including the flight engineer, navigator, and a stewardess, evacuated through the forward service door; 28 evacuated from the left wing, including at least two stewardesses and three JAL male employees; 25, including the first officer and a stewardess, occupied the inboard raft on the right wing; and nine, including the captain, purser, and two stewardesses, occupied the outboard raft on the right wing. [Pages 23-24 (numbered as 21-22).]

(My emphasis, and the passengers and crewmembers who evacuated from the forward doors and the left wing also disembarked into rafts; it's just that each forward door [and the left wing] had just one raft each, so, for these exits, there was no need to distinguish who got into what raft, unlike the situation with the right wing.)

Commercial jet flight: a scheduled JAL flight in a DC-8-62.  Check.
After 1945: occurred in November 1968.  Check.
Carrying paying passengers: 96 of them.  Check.
Minimum aircraft capacity 50 persons or more: there were 107 on board, including 96 passengers, and Wikipedia gives the maximum passenger capacity of a DC-8-62 as 189.  Check.
Raft(s) stored inside cabin pre-deployment: in ceiling compartments above the aisle (similar to those in the 737 in the photo in the OP's question).  Check.
Raft(s) actually designed, and put there, for that purpose: see previous bulletpoint.  Check.
Raft(s) worked as intended: well, everyone on board evacuated into the rafts uninjured, and nobody drowned.  Check.

How can you post about this incident and not mention the Asoh defense, aka "I f___ed up"? :)


text:
How did the Caproni Ca.60 electrical communication system work?
On the wikipedia page for the Ca.60 it says:

The two nacelles also housed a cockpit for one flight engineer each, who controlled the power output of the engines in response to the orders given by the pilots by means of a complex system of lights and indicators located on electrical panels.

I would like to know more details of how this system worked, such as what the function of the switches were, and what was communicated with the lights.
If nobody knows how this particular system worked, maybe we can infer how this worked from similar systems used in the past, if any existed?
There is a picture of the remains of this panel on the wiki page. Here is another picture that I found. Any ideas?


text:
How can an F-22 Raptor reach supersonic speeds without having supersonic inlets?
The F-22 Raptor and some other jets do not have inlet spikes, yet they are able to achieve supersonic speeds. How is that possible?

The F16 as well.

power, a lot of power.

The inlet spike is not required for supersonic flight, it is just one way to minimize the losses that comes with decelerating supersonic flow. As a general rule, the shallower angle that you force the flow to turn at supersonic speeds, the weaker the shock wave that will form at turn, and the lower the loss (in total pressure) will be. This is why the planes are so pointy. The cone that you see on many supersonic inlets is there to provide a gentler deceleration (ie, cause weaker shocks to form), and is often adjustable to optimize this deceleration for different flight mach numbers (shockwaves will form at different angles depending on flight speed). The flow will continue to decelerate through the internal part of the inlet, and will sometimes still be supersonic until a certain part of it depending on the specifics of the design. In this case, contrary to what Carlo Felicione claims, there may still be a shock standing inside the inlet to decelerate the flow finally to subsonic speeds.
The image below shows different ways to design an inlet. Noting the first image, its possible, but very lossy to have you inlet without any forward component that provides gentle external deceleration. The image shows a system of oblique shocks forming inside the inlet, but the other event that could occur with this geometry is that a strong normal shock would stand at the front of the inlet, instantly decelerating the flow to subsonic speed (the image may be wrong here, maybe someone can elucidate in the comments). The first supersonic jets were designed in this way. The two cases on the right show how oblique shocks can be induced to decelerate the flow with less loss compared to the normal shock induced in the first case. The forward parts could be provided by a cone, or simply the side of the aircraft. The furthest right case shows a way to design for shock ingestion in your inlet. You will note that on most modern supersonic jets, the inlets are not the furthest most point of the aircraft.

the F-22 uses the type of inlet shock system of either the right or second to right most design, but probably only the designers know the specifics to be sure.
As an aside, just because there is no external variable geometry, like Carlo Felicione pointed out, doesn't mean there is no active component to the internal geometry (I bet there is). This could include a variable sized throat, or some sort of bleed system to allow for setting up the specific shock system that the designers want for least losses.
image source:https://www.sciencedirect.com/science/article/abs/pii/S1270963819302834 (i found it on google images so I didn't actually open the paper, although it seems like it would be a good reference for this topic)

What is the maximum air flow velocity Turbojet Engine compressor can ingest without shock formation, provided that there is no air flow deceleration i.e using only serpentine ducts as in F-22, F-16, Su-35 etc?

The jet uses a fixed, rhombohedral shaped jet intake combined with a serpentine intake duct.  It allows for speeds just north of Mach 2 without the need for a variable geometry inlet to prevent shockwave ingestion.


text:
How often do jet-liners have touch and go landings?
I read that a go around is 1-3 out of every 1000 and I wondered how rare it is for a large commercial plane to actually hit the runway before deciding to go back up again.

I've done approximately 45 in one B737 in a single day once, but that was a rare occasion of pilot training (I was a guest/observer).

The decision to go back up again is usually made before the aircraft touches the runway. Making the decision to go around after the wheel touch the ground is dangerous because of automatic spoiler deployment and autobrakes which make going around difficult. See for example EK521. Pressing TO/GA before touching down switches the autospoilers and autobrakes off, so a touchdown after the decision is not so much of issue, yet still a very rare occasion.

@DeltaLima, Not to mention that many airline's SOPs require full brake and tire inspections after a go around after it's hit the deck! One Australian airline even requires the wheel and brake assembly be removed, delaying flights and ops.

Quite rare.
An approach abort that results in touchdown is called a "balked landing" and generally happens when you've started the landing transition, reducing power and starting the flare, where you are in a "low energy state" (speed decelerating below Vref and engines going to idle) at the time you make the go-around decision.  It's considered a high(er) risk maneuver like high speed rejects on takeoff, because at that point you are likely going to touch down, however briefly, whether you want to or not.
Normal missed approach go-arounds happen mostly because of weather where the runway environment wasn't visible at minimums, and maybe occasionally from a runway incursion that is noticed early, or something like a report of a flock of birds in the way, which would be most of those 1-3 per 1000 landings.  They happen at at least a hundred or couple hundred feet and usually don't involve actually touching down.
A balked landing will generally only be for something like a runway incursion at the last second, leaving you with a situation where landing and rolling out is obviously more dangerous than going around because you are probably going to hit something on the runway, and they are pretty rare events.  Balked landings are usually special maneuver covered in the initial type course and may be included in recurrent training.

Your assertion of “rare” is generally true, in my opinion, but some stats, outside sources, or even a validation of your industry expertise would improve your answer. Most of what you offer holds true for the light aircraft fleet, apart from intentional touch and gos, but maybe less true for the “jet-liners” in question. In my first and second hand experience, I would suggest automation or guidance issues, unstable approaches, gusty winds, and missed approaches during auto-land to be factors that figure largely in unintentional touch and go landings.

Way more information than needed.  The poster mentioned T&G in the question, but the body was clear he was asking about go-arounds that involved ground contact. It's not a light aircraft thing.  I've done balked landings in sim training in jets (RJs).  It's a dedicated procedure, separate from the normal go-around routine and affects big airplanes with lots of inertia and laggy power response.  I couldn't find any data on balked landings vs missed approaches,so tribal knowledge is all there is to go on.  Admittedly the "rare" bit is what I would call informed opinion but that's all there is.

Industry personnel would have access to actual data to be able to answer this question with specificity, though the data itself may be protected or confidential.


text:
Can you please explain aircraft spin in simple non-mathematical terms?
Can you please explain aircraft spin in simple non-mathematical terms?

Or better yet, just describe what you think you understand about spin and if possible what aspects don’t make sense.

Please rephrase your question to meet the quality standard as explained in the help center. For example, you can read how it flies?, and then come back to precise what part of the spin mechanism you don't understand.

Honestly I am almost at a loss for words here regarding the comments above.  While for the mathematically inclined equations can be useful in enhancing understanding, for others they can be an obstacle.  It really isn't that difficult to share basic knowledge about advanced concepts with others who may not have an engineering or math degree.  That's all the OP is asking for.  Unclear?!  If you are really that confused about how to answer, take a look at below.  Maybe not perfect, but a pretty solid layman's answer to a very simple question if you ask me.

@MichaelHall Am totally with you. Let’s treat new users in a condescending way, because that will make us look good. Ehm...

Not sure if a "non-mathematical" explanation = condescending.  In fact, I would consider making it an Abstract requirement for submission of a question and/or answer (shows understanding before math is applied).  Aircraft operators (pilots) need instructions distilled down to the simplest form AFTER all aspects are thoroughly examined.  (Although new knowledge can lead to improvements) and (don't forget what the OP asked for: simple non-mathematical terms).

Explanation of spin mechanism without maths exists on internet. I agree they are not all clear, and thus question is useful. Yet, asked as is, it may show a lack of basic research. A better way to ask this question may be a link to one of the explanation highlighting the unclear parts.

"A better way to ask this question may be a link to one of the explanation..."  I would suggest the opposite, that a better way to ANSWER the question would be to provide a link.  As you yourself so helpfully did in the comment above.

A spin is a kind of aggravated stall in which one wing becomes more stalled than the other one.  This imbalance in lift results in an autorotative motion abound a vertical axis, generally passing through the inboard wing of the aircraft.  Spins can be initiated be stalling the airplane in a uncoordinated turn, which causes the inboard wing to enter a deeper stall than the outboard wing.  An airplane must always 1) be in an aerodynamic stall in 2) uncoordinated flight in order to enter a spin.

"More stalled" is somewhat misleading, since the outer wing may well have attached flow

More stalled ie at a greater angle of attack

The simplest answer may be: An airplane spins as a result of being uncoordinated when a stall occurs. Uncoordinated means the nose and tail of the airplane are not inline with the flight path. So if the airplane is moving in one direction, but the airplane is pointing in another direction, then it is likely to spin in the event of a stall. That is the simple explanation. The deeper life saving explanation is contained in the video linked here.
This video explains common false notions about how an airplane works that can cause a pilot to stall and spin his or her airplane. Understanding these can help keep you safe when flying. Covered is the skidded turn which is the most common cause of spins. There is some math on how to calculate stall speed for various bank angles, but you can just skip over it if you are not interested. Please let me know if you have questions after watching.
Thanks, John


text:
Can US pilots fly VFR OTT and/or VFR at night in Canada without additional ratings?
In the US, private pilots flying under VFR are implicitly allowed to fly without visual reference to the ground, eg. over an overcast cloud layer, as long as they maintain appropriate VFR weather minimums. The same is true for flying VFR at night.
In Canada, a separate add-on "VFR OTT" rating is required in order to operate "over the top", and there's also an add-on rating for flying VFR at night.
US pilots can operate Canadian-registered aircraft through a Foreign License Validation Certificate, which as far as I can tell confers the privileges of one's native certificate. According to the ICAO, "certificates of competency and licenses issued or rendered valid by the contracting State in which the aircraft is registered, shall be recognized as valid by the other contracting States".
So the question is: do US pilots operating Canadian-registered aircraft via a FLVC need additional ratings to fly VFR over-the-top or at night in Canada, or are the inherent privileges of their US pilot certificate extended to Canada as well?

Welcome to aviation.SE!

It looks like if you have a foreign instrument rating you automatically have VFR OTT privileges, but for night VFR you still need a Canadian night rating.
CAR 421.44(7) for VFR OTT:

An applicant who holds or has held an instrument rating issued by a
  Contracting State shall be considered to have met the Knowledge,
  Experience and Skill requirements specified above

As for night VFR, 421.42 doesn't have any equivalent section that gives credit for foreign qualifications.


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What would the altimeter indication be through a cold front?
Cold air is heavier than hot air because of its greater density, so the QNH of an airport inside a cold front would be higher. Flying towards the cold front would be, "low to high, hello sky".
But I also know that for altimetry, cold air generates lower pressure inside the pitot-static system than warm air, and it would increase the altimeter reading, so "hot to cold, look out below".
I'm confused because of the 2 contradictory factors. If we fly towards a cold front without adjusting the altimeter setting, would there be an increase or a decrease in the indicated altitude?

There's an ATP question:

Event after an aircraft passes through a front into the colder air.

Answer:

Atmospheric pressure increases.

Well, yes, that's why QNH would be higher, but our altimeter would sense the temperature and "feel" a decrease in atmospheric pressure.
So, what would be the real indication of the altimeter in this situation?

This question and many answers below are really bothering me, as I subscribe to this theory and practise: https://aviation.stackexchange.com/questions/43473/how-will-the-altimeter-read-in-air-colder-than-isa . I'm especially bothered, since I've been just told by my peers that ISA is not that big a deal in aviation :) ...ok but seriously, maybe time for chat about this? Anyone?

"For altimetry, colder air generates lower pressure inside the pitot-static system than warm air" may be the source of your confusion.
We are taught the gas law PV= nRT.  The application that lower temperature lowers pressure is valid for a CLOSED container, not for the atmosphere we fly in.
If you reduce the temperature (as weather over a region),  you increase the air density, all other things (such as altitude) being equal.  This results in a lower altimeter reading for the same altitude when passing INTO a cold front.
A study of barometer trends as cold fronts pass at the same altitude (the ground you are standing on) should confirm these thoughts.
Regarding the reverse case, flying into warmer air, it's "high to low, look out below!".  That is the one we need to look out for (gives higher altitude reading than where the aircraft actually is).
This is why it is never a bad idea to radio in for the barometric pressure at your landing site if weather changes significantly.

There are two altimeter reading questions here, what happens when:

flying towards the cold front (third paragraph)
flying into the cold front (headline)

According to this University of Illinois web article following things happen:
Flying towards a cold front (or in the article the front is approaching you, but it makes no difference):

pressure drops steadily
temperature is steady

Passing through the front:

pressure reaches minimum, then rises sharply
temperature drops suddenly.

So, to answer both questions, assuming you are flying at relatively low altitude and maintaining it in reference to your altimeter and you do not adjust QNH:

Approaching the cold front you would steadily drift downwards: from high to low, look out below!
Passing through the front you would need to climb to maintain steady altimeter reading: low to high, hello sky!

You see, the question is about what happens to altimeter reading, but since the vertical position of the aircraft is maintained in reference to the altimeter reading, whether it's you or the autopilot flying, the altimeter reading would not change. The vertical position of the aircraft would be instinctively or algorithmically adjusted to keep the reading at a selected value.
What happens at altitude, is (for now) somewhat beyond me (pressure gradients and stuff), so  I dare not answer that scenario here yet.

P.S. a private pilot should not fly through a cold front: it's not a good place for small planes to be in...

The truth of it is always the simplest.....
Since you are flying and registering your height by your Altimeter there will be no change in your altitude at all.
However, if you wish to know if your height above the ground after flying through a cold front that too could be a poser....
You would need to know how you are crossing the isobars....
Put it most simply then pressure generally would increase along the flight path unless you were flying on a course towards the low centre ( in this regard you would need to draw a hypothetical set of isobars and plot a hypothetical course across the cold front ).
You will see that you can maintain the similar pressure or also actually have it decrease or increase depending on your track.
Flying from high to lower pressure whilst maintaining altimeter reading and local altimeter setting would result in a descending path...
Mnemonic....High to Low....Look out BELOW....
Ouch.....

The altimeter reading is closer based on pressure than temperature.
A cold front is a low pressure system and will affect your altimeter.  If you reduce the pressure on your altimeter your altitude indication will decrease.
If you are flying at 500 ft with a setting of 29.92 and fly into a cold front that has a pressure of 29.00 you will show an increase in altitude on your altimeter even flying straight and level.  But once you call the nearest airport and get the local pressure and set to the new local pressure your indicated altitude will return to 500 ft(ish).

Well, I think you have a wrong point of view. If you fly from warm air mass into colder air your altimeter will read the same. It indicates pressure altitude so it does not matter what the density of the surrounding air is. Your reference is the assigned pressure altitude and that is remains constant.
But the thing is that the cold air is more dense than warm so, as you suggested, your true altitude is lower in the cold air mass. Should there be any obstacles you should increase your indicated  altitude so that acceptable obstacle clearance remains.
If we turn the situation around and you actually would maintain your true, physical altitude constant some how, the indicated pressure altitude would be higher in the cold air mass.
The QNH is not directly affected by the cold air. The QNH is always referenced to airport altitude so on the ground altimeter always displays airport elevation regardless of the air temperature.
Another question is the weather phenomena that cause extremely cold temperatures. When temperatures go below -20C it is often caused by local high pressure accompanied by arctic air mass from the polar region. I’ve seen QNH over 1050 with very cold temperatures.

you have it right.  The third paragraph isn't "turning it around" though, it is the actual case, as the pilot would (generally) maintain heading.  So the altimeter would show a decrease in altitude (greater pressure) even though the plane did not dive.

"If we turn the situation around and you actually would maintain your true, physical altitude constant some how, the indicated pressure altitude would be higher in the cold air mass." - This flatly contradicts the "ATP question" quoted in the question without giving any explanation. Can you explain why the ATP question is wrong?

Also: "If you fly from warm air mass into colder air your altimeter will read the same." - Just to clarify, you're saying that your altimeter will read the same if you're flying at a constant indicated altitude, right?

Yeah, flying constant indicated altitude would be the “real life” case. There is no practical means to maintain constant physical altitude when temperature of the surrounding air changes. But yes, that is the case asked in the question.

From a practical sense, remember:
From high to low, look out below.
If your barometric pressure and/or your temperature goes down (either/or), your altimeter will read a higher indicate value than the actual MSL true value. You will be at a lower altitude than you think.
Ex. Check the Pressure and Density Altitudes at an airport reporting METARs over time. The reporting equipments actual elevation never changes (or at least it shouldn’t). Yet the Density Altitude will change even in conditions of similar barometric pressures.


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Exceeding VLO and by how much is too much?
Piper Seminole (PA-44-180) VLO (max gear retraction speed) is 109 KIAS. I've heard that manufacturer published limitations are significantly lower than actual structural and system limitations. What are the potential repercussions of retracting gear at 10, 20, 30 KIAS over VLO?

VLO is the maximum gear extended speed, not retraction. Is that what you mean?

I think he just means forgetting to retract on climbout and finding himself too fast with the gear still down.

No. VLO is what I meant - the maximum speed at which the gear may be operated. In the case of the Seminole, that’s 109 KIAS. The maximum extend speed is 140 KIAS and that’s VLE. Hope this makes sense.

The gear itself and its attachments being pretty beefy, you can't really damage the gear legs extending them at any speed the airplane can fly at.
The limitations usually relate to the doors, which are more delicate, and having large surface area, are far more affected by air loads.  So the main effect of exceeding a gear speed limitation is the risk of bending or distorting, or in extreme cases blowing off, gear doors.
If you have a minor exceedance of 10kt, I'd just give a visual check of the doors later.  If it was a major exceedance of 20kt or more a tech should look at it. The doors may look ok at a glance, but if they are deformed they can prevent the gear from extending next time, if, say a distorted door's edge overlaps the opening and slips past on retraction but hangs up on extension.
Extension/retraction speeds, VLO, or speed you can operate the gear selector, and maximum operating speed with the gear down, VLE, or speed you can fly with the gear down and locked, are sometimes different (VLO is normally lower than VLE if they are) because there is a limit speed that affects the gear while in transit, whereas once down and locked you can speed up.  This can be from sequenced gear doors that are only open during the extension/retraction cycle, or a limitation on the ability of the hydraulic system to retract, say, a forward retracting nose gear against air loads (a speed limitation could also be related to a stability and control issue as well).
I dimly recall from my multi training days (but not totally sure) that the limitation on the Seminole was related to its rather weak hydraulic pump which had to work too hard above a certain speed, stalling the pump or popping the CB, something like that.  Some amount of safety margin would have been applied to the speed the problem was happening at, giving the published limitation of 109.

Thank you so much for this. It makes perfect sense for the extend limitation. But what about the retract limitation of 109? The POH says you shouldn’t retract the gear above 109 KIAS.

I added some extra context.

Thanks so much! The clarification on the Seminole was exactly what I was seeking. I, unfortunately, busted my Multi Comm ride today because I retracted at 113 vs 109 after recovering from an emergency descent. Live and learn.

I blew my initial IFR ride and had to redo part of it.  If you aren't using a home computer sim to practice and drill your training at home, you should be.


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What are the concerns and consequences of an overweight landing?
If a 777 ER has to immediately land after takeoff on a planned 14,594 km trip (in the case of a fire, e.g.), the landing will be executed with a very heavy aircraft.

What are the major concerns of doing such a landing?
What will, on average, be the consequences of this overweight landing?

Because it's an emergency, you're likely to already have a "problem" on top of the fact you'll have to conduct an overweight landing. Depending on the emergency, you can add much more concerns and consequences to the main ones explained in the answers below. (Fire: engine fire ? hydraulic failure due to a fire ? etc.) By the way, fire fighters can't properly work on a landed aircraft if there's a risk to make passengers suffocate under foam (hence evacuation duration) Brakes will overheat. Better not have leaking fuel nearby; heartbeating with a 777 full of fuel... 14594km.. quite precise :P

Max landing vs. takeoff weight

Aren't there systems for dumping fuel? I believe that you could significantly decrease the weight by this measure alone, even in a short time. Reference

Now of course in the case of catastrophic failure of main components on take-off for a long range flight this might not be possible, as there can be tens of tons of fuel that needs to be jettisoned.

Seems like I read on another question that when an overweight landing happens, the plane has to undergo mandatory maintenance or inspection, but I can't find that now.  Am I making this up?

@JPhi1618 a special inspection is required after any event outside of the limits for which the plane was certified. See https://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/amt_handbook/media/FAA-8083-30_Ch08.pdf page 8-16.

Two things:

Loads on the landing gear. This can be alleviated by carefully touching down, but you never know what exactly will happen in the next landing, so better don't count on it to be smooth
Deceleration distance: The higher mass requires a higher approach and touch down speed (higher by the square root of the mass ratio between your actual mass and the maximum certified landing mass). Now you have more mass and more speed, but the landing strip and the airliner's brakes are still the same. The risk is that you overshoot the runway with an airplane full of fuel or that you overheat the brakes (which will result in their failure, and again an overshoot). Since the kinetic energy is proportional to mass times speed squared, the energy which needs to be absorbed by the brake goes up with the square of the mass increase.

If the selected runway for your overweight landing is long enough and the weather is calm (so a smooth landing is easier), an overweight landing is not such a problem.
Now let's look at the 777-300ER in detail. I use the figures from Wikipedia, because the manufacturer's site is trying much harder to hide the relevant data. The MTOW (maximum take-off weight, which is actually a mass) is 351,534 kg, and the maximum landing weight is 251,290 kg, about 100 tons less. Now let's assume that taking off and returning to the airfield uses 5 tons of fuel, so the mass ratio is 1.379. Therefore, the approach speed has to be 17.4% higher and the total kinetic energy at touchdown is higher by a factor of 1.9 compared to the case at maximum allowable landing weight.
If we now assume that speed is reduced linearly during the landing run and that the wheel brakes will just absorb as much energy over time as in the case at maximum landing weight, the deceleration needs to be lower by the mass ratio, so the aircraft decelerates with only 72.5% of the deceleration at maximum landing weight. To shed its kinetic energy, the landing run will take longer by the increase in kinetic energy, i.e. 1.9. Since the average speed is also higher by 17.4%, the landing distance will be higher by a factor of 2.233 or 223% of the landing distance at maximum landing weight.
This neglects that the heating of the brakes is an instationary process, so you cannot simply brake with the same intensity for more than twice the time they were designed for. But this little estimation should illuminate what impact a higher landing mass has on the energy and distance involved.

Re: loads on the landing gear, are you talking about landing gear collapse, tire puncture or what?

@JonasG.Drange, when the vertical momentum is more than what the shock absorbers can handle, the shock transfers to the surrounding structure, which usually gets damaged before the gear would collapse. Not so much that the airplane would fall apart, but such damage is usually very hard to repair.

@JanHudec What happens to the plane next day and after is probably a little a concern if you have an emergency now, right? :D

@JanHudec Sometimes the landing gear does fail from excessive loads, though, which results in undesirable consequences right now (though it might actually reduce your stopping distance a bit, since a 777 fuselage/runway surface interface produces quite a lot of friction.)

@reirab, that is the nose gear, which is way more fragile though. But the main gear usually only gives if there is a preexisting crack in it or if the landing is really hard, while I've seen couple of hard landing reports where the gear held, but other parts of the structure got damaged.

@JonasG.Drange as well as the loads on the landing gear, don't ignore the fact that landing a plane which is 30% overweight is equivalent to landing a plane were all the tires are 30% under-inflated. You probably wouldn't want to drive you car in that condition, let alone land a plane!

@alephzero: Not true. The same airplane just took off on the same tires with the same load. And take-off speed is higher than landing speed. Unless the pilot slams the plane into the runway, the tires and gear will be fine. Note that static load means typically 2/3 of oleo deflection. The problem is the brakes and the long distance needed for deceleration.

@PeterKämpf But the dynamic loads on touchdown will be higher than static while you are compressing the oleos (even for a normal touchdown), the landing speed for a heavy plane will be faster than for normal weight, and the braking forces have to go through the tire walls and treads. You may be right but it's not "obvious" (at least to this mech engineer!) that everything would be OK.

Is runway length actually an issue if you're returning to a runway that would have had room for a V1 rejected takeoff at the same mass?

@HenningMakholm: Good question! My reference is this, page 3-13. It gives the sea level T-O field length as just a tad above 10,000 ft and the landing distance as 6,100 ft (page 3-29). So the runway length is indeed an issue - the overweight landing (using only brakes and my scaling) will eat up 13,600 ft!

@PeterKämpf: The reason why that result surprises me is that the tables I could google up suggest that Vr is generally less than 10% above V1 for a departing 777. Assuming that it is possible to touch down with at most Vr speed (which at least sounds plausible to me) and the braking effect afterwards is the same as for a rejected takeoff, the runway length needed to land should only be 1.3 times the remaining length after the V1 point during takeoff. (In a constant-power acceleration, the distance goes as the cube of the speed).

@HenningMakholm: $v_r$ is below minimum flight speed as the aircraft accelerates through the rotation phase. But with TO flaps the minimum speed is higher than with full flaps, so you have a point here. Now the fastest phase of the take-off and landing will eat up most runway length, but still, I agree that a rejected take-off should need similar space - after all, all the acceleration before also needs some runway length. Landing distance is measured from 35ft high with 1.3·$v_{min}$, but still ... please consider to post this as a new question.

@PeterKämpf: Actually that 1.3 safety factor for landing speed does seem to explain the discrepancy. With a constant-power deceleration, "1.3 times as fast" translates to "2.2 times as far" before coming to a halt, which is broadly consistent with your estimate.

Boeing has provided detailed documents online, the website has not shown because it mainly used for advertisment/promotion. http://www.boeing.com/assets/pdf/commercial/airports/acaps/777_2lr3er.pdf

The major issue with landing a plane that is overweight is over-running the runway.
If you are trying to land a plane that is over it's rated landing weight, you will need to be going faster to keep enough airflow over the wings to generate the lift required to keep the plane in the air. This, of course, has the consequence that it will take longer to stop when on the runway.
Another factor that contributes to it taking longer to stop when on the runway is that the extra weight of the plane adds to the momentum. The calculation for momentum is p=mv where m is mass and v is velocity (for this example we can think of it as speed.)
So not only are we now landing with a higher mass (m) we are also landing with a higher speed (v) so our momentum increases very quickly.
For example, if we had a plane that was 660,000 pounds, and needed to travel at (lets say) 290km/h (156 knots) to keep giving enough lift, it's momentum would be:
191400000 pounds km/h
If we look at a normal landing weight and speed of a 777 524,000 pounds landing at a normal speed of 250km/h then the momentum would be:
135500000 pounds km/h
you can see that even a small increase in speed causes the momentum to increase significantly.
The other issue is the load put on the landing gear which have the potential damage them, although I think that the deceleration speed is the bigger factor here.
(I am not a mathematician, my calculations may be wrong so feel free to edit the answer if I did get them wrong)
EDIT: One other thing I forgot to mention was that most larger airports have a special kind of surface at the end of the runway that serve to slow planes. They are constructed (iirc) out of some sort of very strong foam like material that is very effective at slowing a plane. I don't remember exactly what it was made out of though.
As mentioned by NoviceInDisguise and ChrisW, this is actually called the Engineered materials arrestor system and is made out of lightweight, crushable concrete blocks.
You can see an image of the effect here where the plane's wheels have dug through the soft layer which helps slow the plane.:

Momentum is not very important here. More important is kinetic energy which has to be converted to heat in the brakes (and brakes heated to 900°C are not funny). Kinetic energy grows with mass and square of speed, but since landing speed only grows with square root of weight, energy of landing plane grows with square of its mass. It is still an awful lot.

I believe they use a form of aerated concrete.

Wikipedia: Engineered materials arrestor system

Yep, that's what I was thinking of. I'll add it to the answer.

An overweight landing is defined as a landing made at a gross weight in excess of the maximum design (i.e., structural) landing weight for a particular model.
In general, landing overweight (though not desirable) is safe. FAA has stated:

There has been no adverse service experience with airplanes certificated under Part 25 involved in overweight landings.

The major concerns for overweight landing are:

Loads on the Landing Gear The touchdown rates are higher in case of overweight landings. Touchdown at higher-than-normal sink rates may result in structural limits being exceeded.
However, unless the pilot does a very hard landing, this should not be a problem. This is because regulatory requirements for landing gear design are based on a sink rate of 6 feet per second at the maximum design takeoff weight, while the usual sink rate is nearly half of that.
Also, the wheel, brake and tire design is based on the most severe landing stop conditions at maximum wear out or a rejected landing at maximum take off weight, whichever is worse.
Landing Field Length This becomes an issue only when the selected runway is smaller than the requirements. As the landing weight increases, the approach and touchdown speeds increases and the aircraft require more distance to decelerate.
The landing length required is more as the weight increases and the aircraft field lengths are calculated for landing at MTOW. For example, for 777, according to Boeing, excess field length is available even for landing at MTOW.

Image from Overweight Landing? Fuel Jettison? What to Consider

Performance Higher weight involves performance penalties as the control forces required are more.
Control In most aircraft, for example in Boeings, the autopilot is not certified for overweight landings.

In case an overweight landing has been carried out, there are some inspections required to be carried out:

Phase I The aircraft is inspected for obvious signs of structural distress, such as wrinkled skin, popped fasteners, or bent components in areas which are readily accessible.
Phase II This is a much more detailed inspection required in case the Phase I inspection shows signs of excessive stress and requires opening access panels to examine critical structural components.

In general, overweight landings should pose no problems as long as the landing is performed correctly.

Sorry to catch it so late. rejected landing at maximum take off weight I have only heard of rejected takeoff at MTOW. Am I missing something?


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Why is the phrase “infinite energy” used by this (alleged) ATSB investigator?
In the Air Crash Investigation episode, “Titanic In The Sky”, a Quantas Airbus A380 suffers an uncontained engine failure which partially cripples the plane. In the investigation part of the episode, an “ATSB Investigator” says that:

[…] the fragments [from the rupture of the fanblade] are released with an infinite energy, which means that there's nothing that can stop the engine pieces¹.

Did he forget to add virtually, or is the ATSB just not very accurate when they talk about these incidents on TV? Or is this terminology actually used in aviation contexts?
If you accelerate an engine blade to have infinite energy, hydraulic failures would be the least of your worries².
It should be noted that I cannot find unlimited or infinite in the preliminary ATSB report.

I believe that was either a paraphrase of the report for dramatic effect, or a quote from an unofficial source, rather than the actual report.

Us Aussies are prone to exaggeration ;)

You are correct in that this is not a quote of the report -- the final report does not use that phraseology either.  What the investigator means is that the energy is effectively infinite, as it is impossible to stop something with that much kinetic energy within the mass budget of an airplane engine cowling.